An anti-theft RFID system for monitoring the presence of a plurality of tagged items includes an RFID reader including an antenna and being configured to transmit an interrogating signal to the RFID tags and retrieve data; a processor configured to process the data that the RFID reader retrieves from the RFID tags; and a display connected to the processor and configured to display a result processed by the processor. The processor is configured to update a first counter value indicating the number of tagged items located within a predefined area and to update a second counter value indicating the number of tagged items being taken away from the predefined area. The display is configured to display the values of the first and the second counters and thereby to assist an operator to determine the occurrence of a security event by analyzing the values of the first and the second counters.